Akuma na Kuchibiru

A high-school student named Hana Yamada feels unwell after a gathering and leaves early. On her way home, she meets a handsome man who assists her but misidentifies her as a middle schooler before departing. The following day, Hana visits the nurse’s office and discovers that man there—Shuuji Kido. Initially charming in appearance, he is later revealed to be a strict teacher.